The Elder Scrolls V: Skyrim Glitches

Ghostly Remains in the Air
Upon the completion of Save: Winterhold during the completion of the College of Winterhold, you will be asked to defeat the ice ghosts the invade and threat the town. After killing them their "ghostly remains" will continue to stay where they were killed; whether that be in the air or on the ground. The remains are unable to be moved or erased.